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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-07 02:04:06 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-07 02:04:06 +0000 |
| commit | 5dff2d61cc1c27747ee398e04d8e02843aabb1f8 (patch) | |
| tree | a67c336b406c8227bac912beb74a1ad3cdc55100 /docs/manual/mod/mod_proxy_hcheck.html.en | |
| parent | Initial commit. (diff) | |
| download | apache2-5dff2d61cc1c27747ee398e04d8e02843aabb1f8.tar.xz apache2-5dff2d61cc1c27747ee398e04d8e02843aabb1f8.zip | |
Adding upstream version 2.4.38.upstream/2.4.38upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'docs/manual/mod/mod_proxy_hcheck.html.en')
| -rw-r--r-- | docs/manual/mod/mod_proxy_hcheck.html.en | 274 |
1 files changed, 274 insertions, 0 deletions
diff --git a/docs/manual/mod/mod_proxy_hcheck.html.en b/docs/manual/mod/mod_proxy_hcheck.html.en new file mode 100644 index 0000000..46ec9cc --- /dev/null +++ b/docs/manual/mod/mod_proxy_hcheck.html.en @@ -0,0 +1,274 @@ +<?xml version="1.0" encoding="ISO-8859-1"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head> +<meta content="text/html; charset=ISO-8859-1" http-equiv="Content-Type" /> +<!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>mod_proxy_hcheck - Apache HTTP Server Version 2.4</title> +<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> +<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> +<link href="../style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="../style/css/prettify.css" /> +<script src="../style/scripts/prettify.min.js" type="text/javascript"> +</script> + +<link href="../images/favicon.ico" rel="shortcut icon" /></head> +<body> +<div id="page-header"> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p> +<p class="apache">Apache HTTP Server Version 2.4</p> +<img alt="" src="../images/feather.png" /></div> +<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div> +<div id="path"> +<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.4</a> > <a href="./">Modules</a></div> +<div id="page-content"> +<div id="preamble"><h1>Apache Module mod_proxy_hcheck</h1> +<div class="toplang"> +<p><span>Available Languages: </span><a href="../en/mod/mod_proxy_hcheck.html" title="English"> en </a> | +<a href="../fr/mod/mod_proxy_hcheck.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p> +</div> +<table class="module"><tr><th><a href="module-dict.html#Description">Description:</a></th><td>Dynamic health check of Balancer members (workers) for +<code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code></td></tr> +<tr><th><a href="module-dict.html#Status">Status:</a></th><td>Extension</td></tr> +<tr><th><a href="module-dict.html#ModuleIdentifier">Module Identifier:</a></th><td>proxy_hcheck_module</td></tr> +<tr><th><a href="module-dict.html#SourceFile">Source File:</a></th><td>mod_proxy_hcheck.c</td></tr> +<tr><th><a href="module-dict.html#Compatibility">Compatibility:</a></th><td>Available in Apache 2.4.21 and later</td></tr></table> +<h3>Summary</h3> + + <p>This module provides for dynamic health checking of balancer + members (workers). This can be enabled on a worker-by-worker + basis. The health check is done independently of the + actual reverse proxy requests.</p> + + <p>This module <em>requires</em> the service of <code class="module"><a href="../mod/mod_watchdog.html">mod_watchdog</a></code>.</p> + +<div class="note"><h3>Parameters</h3> + <p>The health check mechanism is enabled via the use of additional + <code class="directive"><a href="../mod/mod_proxy.html#balancermember">BalancerMember</a></code> parameters, which are configured + in the standard way via <code class="directive"><a href="../mod/mod_proxy.html#proxypass">ProxyPass</a></code>:</p> + + <p>A new BalancerMember <a href="mod_proxy.html#status_table">status</a> state (flag) + is defined via this module: "<code>C</code>". + When the worker is taken offline due to failures as determined by the health + check module, this flag is set, and can be seen (and modified) via the + <code>balancer-manager</code>.</p> + + <table> + <tr><th>Parameter</th> + <th>Default</th> + <th>Description</th></tr> + <tr><td>hcmethod</td> + <td>None</td> + <td>No dynamic health check performed. Choices are: + <table> + <tr><th>Method</th><th>Description</th><th>Note</th></tr> + <tr><td>None</td><td>No dynamic health checking done</td><td /></tr> + <tr><td>TCP</td><td>Check that a socket to the backend can be created: e.g. "are you up"</td><td /></tr> + <tr><td>OPTIONS</td><td>Send an <code>HTTP OPTIONS</code> request to the backend</td><td>*</td></tr> + <tr><td>HEAD</td><td>Send an <code>HTTP HEAD</code> request to the backend</td><td>*</td></tr> + <tr><td>GET</td><td>Send an <code>HTTP GET</code> request to the backend</td><td>*</td></tr> + + <tr><td colspan="3" /></tr> + <tr><td colspan="3">*: Unless <code>hcexpr</code> is used, a 2xx or 3xx HTTP status will be interpreted as <em>passing</em> the health check</td></tr> + </table> + </td></tr> + <tr><td>hcpasses</td> + <td>1</td> + <td>Number of successful health check tests before worker is re-enabled</td></tr> + <tr><td>hcfails</td> + <td>1</td> + <td>Number of failed health check tests before worker is disabled</td></tr> + <tr><td>hcinterval</td> + <td>30</td> + <td>Period of health checks in seconds (e.g. performed every 30 seconds)</td></tr> + <tr><td>hcuri</td> + <td> </td> + <td>Additional URI to be appended to the worker URL for the health check.</td></tr> + <tr><td>hctemplate</td> + <td> </td> + <td>Name of template, created via <code class="directive"><a href="#proxyhctemplate">ProxyHCTemplate</a></code>, + to use for setting health check parameters for this worker</td></tr> + <tr><td>hcexpr</td> + <td> </td> + <td>Name of expression, created via <code class="directive"><a href="#proxyhcexpr">ProxyHCExpr</a></code>, + used to check response headers for health.<br /> + <em>If not used, 2xx thru 3xx status codes imply success</em></td></tr> + </table> +</div> + +</div> +<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><h3>Topics</h3> +<ul id="topics"> +<li><img alt="" src="../images/down.gif" /> <a href="#examples">Usage examples</a></li> +</ul><h3 class="directives">Directives</h3> +<ul id="toc"> +<li><img alt="" src="../images/down.gif" /> <a href="#proxyhcexpr">ProxyHCExpr</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#proxyhctemplate">ProxyHCTemplate</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#proxyhctpsize">ProxyHCTPsize</a></li> +</ul> +<h3>Bugfix checklist</h3><ul class="seealso"><li><a href="https://www.apache.org/dist/httpd/CHANGES_2.4">httpd changelog</a></li><li><a href="https://bz.apache.org/bugzilla/buglist.cgi?bug_status=__open__&list_id=144532&product=Apache%20httpd-2&query_format=specific&order=changeddate%20DESC%2Cpriority%2Cbug_severity&component=mod_proxy_hcheck">Known issues</a></li><li><a href="https://bz.apache.org/bugzilla/enter_bug.cgi?product=Apache%20httpd-2&component=mod_proxy_hcheck">Report a bug</a></li></ul><h3>See also</h3> +<ul class="seealso"> +<li><code class="module"><a href="../mod/mod_proxy.html">mod_proxy</a></code></li> +<li><a href="#comments_section">Comments</a></li></ul></div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="examples" id="examples">Usage examples</a></h2> + + + <p>The following example shows how one might configured health checking + for various backend servers:</p> + + + <pre class="prettyprint lang-config">ProxyHCExpr ok234 {%{REQUEST_STATUS} =~ /^[234]/} +ProxyHCExpr gdown {%{REQUEST_STATUS} =~ /^[5]/} +ProxyHCExpr in_maint {hc('body') !~ /Under maintenance/} + +<Proxy balancer://foo> + BalancerMember http://www.example.com/ hcmethod=GET hcexpr=in_maint hcuri=/status.php + BalancerMember http://www2.example.com/ hcmethod=HEAD hcexpr=ok234 hcinterval=10 + BalancerMember http://www3.example.com/ hcmethod=TCP hcinterval=5 hcpasses=2 hcfails=3 + BalancerMember http://www4.example.com/ +</Proxy> + +ProxyPass "/" "balancer://foo" +ProxyPassReverse "/" "balancer://foo"</pre> + + +<p>In this scenario, <code>http://www.example.com/</code> is health checked by sending a <code>GET /status.php</code> +request to that server and seeing that the returned page does not include the string <em>Under maintenance</em>. If +it does, that server is put in health-check fail mode, and disabled. This dynamic check is performed +every 30 seconds, which is the default.</p> + +<p><code>http://www2.example.com/</code> is checked by sending a simple <code>HEAD</code> request every +10 seconds and making sure that the response status is 2xx, 3xx or 4xx. <code>http://www3.example.com/</code> is checked +every 5 seconds by simply ensuring that the socket to that server is up. If the backend is marked as +"down" and it passes 2 health check, it will be re-enabled and added back into the load balancer. +It takes 3 back-to-back health check failures to disable the server and move it out +of rotation. Finally, <code>http://www4.example.com/</code> is +not dynamically checked at all.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="ProxyHCExpr" id="ProxyHCExpr">ProxyHCExpr</a> <a name="proxyhcexpr" id="proxyhcexpr">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Creates a named condition expression to use to determine health of the backend based on its response</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyHCExpr <em>name</em> {<em>ap_expr expression</em>}</code></td></tr> +<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr> +<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> +<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy_hcheck</td></tr> +</table> + <p>The <code class="directive">ProxyHCExpr</code> directive allows + for creating a named condition expression that checks the response + headers of the backend server to determine its health. This named + condition can then be assigned to balancer members via the <code>hcexpr</code> + parameter.</p> + + <div class="example"><h3>ProxyHCExpr: Allow for 2xx/3xx/4xx as passing</h3><pre class="prettyprint lang-config">ProxyHCExpr ok234 {%{REQUEST_STATUS} =~ /^[234]/} +ProxyPass "/apps" "balancer://foo" + +<Proxy balancer://foo> + BalancerMember http://www2.example.com/ hcmethod=HEAD hcexpr=ok234 hcinterval=10 +</Proxy></pre> +</div> + + <div class="note"> + The <a href="../expr.html">expression</a> can use curly-parens ("{}") as + quoting deliminators in addition to normal quotes. + </div> + + <p>If using a health check method (eg: <code>GET</code>) which results in a response + body, that body itself can be checked via <code>ap_expr</code> using the <code>hc()</code> + expression function, which is unique to this module.</p> + + <p>In the following example, we send the backend a <code>GET</code> request + and if the response body contains the phrase <em>Under maintenance</em>, + we want to disable the backend.</p> + + <div class="example"><h3>ProxyHCExpr: Checking response body</h3><pre class="prettyprint lang-config">ProxyHCExpr in_maint {hc('body') !~ /Under maintenance/} +ProxyPass "/apps" "balancer://foo" + +<Proxy balancer://foo> + BalancerMember http://www.example.com/ hcexpr=in_maint hcmethod=get hcuri=/status.php +</Proxy></pre> +</div> + + <p><em>NOTE:</em> Since response body can quite large, it is best if used against specific status pages.</p> + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="ProxyHCTemplate" id="ProxyHCTemplate">ProxyHCTemplate</a> <a name="proxyhctemplate" id="proxyhctemplate">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Creates a named template for setting various health check parameters</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyHCTemplate <em>name</em> <em>parameter</em>=<em>setting</em> [...]</code></td></tr> +<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config, virtual host</td></tr> +<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> +<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy_hcheck</td></tr> +</table> + <p>The <code class="directive">ProxyHCTemplate</code> directive allows + for creating a named set (template) of health check parameters + that can then be assigned to balancer members via the <code>hctemplate</code> + parameter.</p> + + <div class="example"><h3>ProxyHCTemplate</h3><pre class="prettyprint lang-config">ProxyHCTemplate tcp5 hcmethod=tcp hcinterval=5 +ProxyPass "/apps" "balancer://foo" + +<Proxy balancer://foo> + BalancerMember http://www2.example.com/ hctemplate=tcp5 +</Proxy></pre> +</div> + + +</div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="directive-section"><h2><a name="ProxyHCTPsize" id="ProxyHCTPsize">ProxyHCTPsize</a> <a name="proxyhctpsize" id="proxyhctpsize">Directive</a></h2> +<table class="directive"> +<tr><th><a href="directive-dict.html#Description">Description:</a></th><td>Sets the total server-wide size of the threadpool used for the health check workers</td></tr> +<tr><th><a href="directive-dict.html#Syntax">Syntax:</a></th><td><code>ProxyHCTPsize <em>size</em></code></td></tr> +<tr><th><a href="directive-dict.html#Default">Default:</a></th><td><code>ProxyHCTPsize 16</code></td></tr> +<tr><th><a href="directive-dict.html#Context">Context:</a></th><td>server config</td></tr> +<tr><th><a href="directive-dict.html#Status">Status:</a></th><td>Extension</td></tr> +<tr><th><a href="directive-dict.html#Module">Module:</a></th><td>mod_proxy_hcheck</td></tr> +</table> + <p>If Apache httpd and APR are built with thread support, the health check + module will offload the work of the actual checking to a threadpool + associated with the Watchdog process, allowing for parallel checks. + The <code class="directive">ProxyHCTPsize</code> directive + determines the size of this threadpool. If set to <code>0</code>, no threadpool + is used at all, resulting in serialized health checks.</p> + + <div class="example"><h3>ProxyHCTPsize</h3><pre class="prettyprint lang-config">ProxyHCTPsize 32</pre> +</div> + + +</div> +</div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="../en/mod/mod_proxy_hcheck.html" title="English"> en </a> | +<a href="../fr/mod/mod_proxy_hcheck.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p> +</div><div class="top"><a href="#page-header"><img src="../images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed again by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Freenode, or sent to our <a href="http://httpd.apache.org/lists.html">mailing lists</a>.</div> +<script type="text/javascript"><!--//--><![CDATA[//><!-- +var comments_shortname = 'httpd'; +var comments_identifier = 'http://httpd.apache.org/docs/2.4/mod/mod_proxy_hcheck.html'; +(function(w, d) { + if (w.location.hostname.toLowerCase() == "httpd.apache.org") { + d.write('<div id="comments_thread"><\/div>'); + var s = d.createElement('script'); + s.type = 'text/javascript'; + s.async = true; + s.src = 'https://comments.apache.org/show_comments.lua?site=' + comments_shortname + '&page=' + comments_identifier; + (d.getElementsByTagName('head')[0] || d.getElementsByTagName('body')[0]).appendChild(s); + } + else { + d.write('<div id="comments_thread">Comments are disabled for this page at the moment.<\/div>'); + } +})(window, document); +//--><!]]></script></div><div id="footer"> +<p class="apache">Copyright 2019 The Apache Software Foundation.<br />Licensed under the <a href="http://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>.</p> +<p class="menu"><a href="../mod/">Modules</a> | <a href="../mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="../glossary.html">Glossary</a> | <a href="../sitemap.html">Sitemap</a></p></div><script type="text/javascript"><!--//--><![CDATA[//><!-- +if (typeof(prettyPrint) !== 'undefined') { + prettyPrint(); +} +//--><!]]></script> +</body></html>
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